NUMERICAL STUDY OF JUICE CONCENTRATION IN THE CONVECTION APPARATUS WITH SWIRLING HEAT-TRANSFER AGENT FLOW

The paper presents a highly potent vortex apparatus for fruit and vegetable juice concentration in the «gentle» regime ensuring the preservation of biologically active substances and high flavor quality of the product. Calculation of the convection apparatus with air tangent vortex generator with the concentrate’s known properties is based on the material and heat balances, together with condition that necessary evaporation time, induced by the process kinetics, should be provided by the chamber and vortex generator constructions, determined by hydro- aerodynamic laws and heat- and mass transfer distinctive features in the apparatus. The main requirement for the concentration termination is to achieve necessary mass content of soluble solids in the product. The designed mathematical model allows us to describe the behavior of an evaporating drop in a swirling gas flow over the wide range of calculated parameters and operating regimes for the vortex camera. Numerical calculation shows that average evaporation time for various drop diameters decreases 8.8 times with circulation ratio increasing from 0 to 5 in the concentrate liquid. The fact of the relative apparatus height reduction under the rise of the average consumed gas velocity in a vortex generator with decreasing blades’ inclination of the vortex generator and a liquid-gas ratio in various cases of the initial liquid drop diameter has been established. The numerical calculation indicates that the narrowing of annular rotating drop layer of liquid on increasing the circulation ratio for «smooth» entering of a drop onto its trajectory needs observance of the principle of equality between the initial drop tangential velocity and gas tangential velocity. According to the calculation, the gas temperature within 105 ± 25°С with liquid circulation ratio over two does not influence significantly the drop trajectory.